1. Field of the Invention
The present invention relates to an electric moisture meter, in particular to an electric moisture meter for measuring and indicating the water content of a sample.
If the quality of a cereal product is to be maintained and the shelf life following the reaping thereof is to be lengthened, the water content thereof is required to be regulated properly. When the moisture content of the cereal product is too low, the taste thereof as a food is deteriorated greatly even though the shelf life thereof may be long, while if the moisture content is too high, on the other hand, bacteria will multiply to cause decomposition thereof.
In calculation of the yield of a cereal product, the moisture content of a small amount of sample thereof is measured to correct the yield. In the case where the moisture content of a 100 g sample collected from a ton of cereal product, for instance, an error of moisture content measurement of 1% by weight will cause an yield error of 10 kg (=1 ton.times.1%).
The forecasting of the yield of cereal products important to our dietary life is essential for enabling us to take action against an unbalanced demand and supply of particular cereal product. Such a forecasting of course greatly depends on the weather and rainfall of the year involved. The accumulated effect of the weather conditions of the year presents itself on the yield of the cereals several months before the reaping thereof, and the moisture content of the sample collected at that time is measured in the same manner as mentioned above. The resultant measurement data will be useful to secure a balanced demand and supply of the cereals in the market thereof.
2. Description of the Prior Art
An electric moisture meter is disclosed in U.S. Pat. No. 4,408,128 dated Oct. 4, 1983, granted to Fujita and assigned to the same assignee as the present assignee. An electric moisture meter is a device operating on the principle that the electric capacity of a sample held between positive and negative electrodes is measured, and the value of moisture content thereof is indicated on the basis of the correlation studied in advance between the moisture content and the electrical characteristics. This correlation varies with the type and quality of a cereal product involved on the one hand and with the country or area of production on the other hand. Due to the variations in grain size, for example, a single moisture meter fails to serve the purpose of all cereal products. There are probably four to five types of cereal products of which the moisture content is to be measured in a single area. It is, therefore, necessary to provide a moisture meter having correlations calibrated for five respective cereal products according to the type or grain size. In order for a moisture meter to be used for an area different from the area where the meter has so far been used, on the other hand, the correlationship contained in the particular meter is required to be changed. Further, the apparent difference in the water content value caused by the differences of temperature at the time of measurement makes correction by temperature desirable.